The present invention relates in particular to a water hydraulic axial piston machine and preferably to a piston machine operating as a water pump.
When in such a water pump the shaft is rotatably driven, for example by an external motor, the cylinder drum rotates as well together with the cylinders and the piston accommodated in said cylinders. Since each piston has a slide shoe which is held in contact with the swash plate and the swash plate has a predetermined or variable angle relative to a normal plane to said axis of rotation, the rotational movement of the cylinder drum drives the pistons back and forth in a direction parallel to the axis of rotation. In order to achieve such a movement it is necessary to keep the slide shoes in contact with the swash plate. The pressure plate is used for that purpose. The pressure plate is loaded by a spring arrangement. The spring arrangement has a number of coil springs which are located within a guiding element having a number of through-going bores, one for each coil spring.
The pressure plate rests usually on a ball element having a bearing surface in form of a sphere. Theoretically, the rotational movement of the cylinder drum should produce a swiveling or pivoting movement of the pressure plate only and therefore the coil springs are loaded by axial forces only. However, in practice it can be observed that forces are generated acting laterally or in circumferential direction around the axis of rotation on the coil springs. This leads to the negative effect that the coil springs contact the guiding element and, after a certain time of operation, works into the guiding element so that a part of the coil spring length gets lost. Furthermore, there is a risk that the coil springs are damaged or broken.